Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-07-08
2002-03-12
Ellis, Kevin L. (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
Reexamination Certificate
active
06356978
ABSTRACT:
The present invention relates to file control devices for controlling external memory devices in information processing systems, and particularly to a file control device for controlling a plurality of disk type memory devices.
In a typical information processing system, a disk sub-system including a plurality of magnetic disk drives and a file or disk control device for controlling the disk drives is normally employed as an external memory system. The disk control device accesses a designated magnetic disk drive in accordance with an access request from a host apparatus. In response, the accessed disk control device transfers the requested data to the host apparatus via the disk control device. Thus, it is highly desirable to have a disk control device which efficiently controls the data transfer between the disk drives and the host apparatus, particularly in view of the rapid progress in the information processing field.
With respect to the structure of the known file or disk control devices, they are typically divided into a plurality of function modules. One such known structure is shown in
FIG. 9
, and generally indicated at
101
. The disk control device
101
is connected between a plurality of host apparatus
102
(one shown) and a plurality of disk drives
103
, and enables the host apparatus to access the disk drives. Any of the disk drives
103
can be used in common by the host apparatus
102
by using the disk control device
101
.
The disk control device
101
is divided into an “a” group and a “b” group, for example. These groups are electrically isolated from each other, but include the same function modules which perform duplicate operations to protect the information processing system against failures. Thus, the description of the function modules generally applies equally to both groups and are made without specifying the particular group to which they belong.
Each of the host apparatus
102
is connected to a corresponding channel adapter (CA)
104
provided in the disk control device
101
. The channel adapter
104
transfers data between the host apparatus
102
and a share storage (SS)
105
which stores the data transferred between the host apparatus
102
and the disk drives
103
, in accordance with commands issued by the host apparatus. In other words, the share storage
105
is generally used as a cache memory for temporarily storing data to be stored in the disk drives
103
or to be retrieved from the disk drives.
Data is stored in the share storage
105
via the channel adapters
104
when the data is received from the host apparatus
102
, or via device adapters (DA)
106
when received from the disk drives
103
. The channel adapter
104
checks, when the host apparatus
102
requests a particular data, whether the object data exists in the cache memory, i.e., in the share storage
105
. The data stored in the cache memory is managed by cache function engines (CFE)
107
a,
107
b,
which are respectively connected to common buses
108
a,
108
b.
The cache function engines
107
a,
107
b,
from both group “a” and group “b” are connected in common to a cache table storage (CTS)
112
which maintains a list of data stored in the cache memory for both groups. By referring to the cache table storage
112
, the cache function engine
107
judges whether the data inquired by the channel adapter
104
exists in the cache memory, and then notifies the result to the channel adapter
104
. If the object data exists in the cache memory, i.e., in the share storage
105
, the channel adapter
104
transfers the data to the host apparatus
102
from the cache memory.
On the other hand, if the object data does not exist in the share storage
105
, the object data must first be stored in the share storage. Thus, upon receiving a response from the cache function engine
107
that the object data is not stored in the cache memory, the channel adapter
104
makes a request to a resource manager (RM)
109
to store the data in the cache memory. This request is also made through the bus
108
. The resource managers
109
a,
109
b
from both groups “a” and “b” are connected in common to a resource table storage (RTS)
113
, which maintains the data regarding the disk drives
103
which are connected to and under the control of the control device
101
, and the arrangement of data in those disk drives.
By referring to the resource table storage (RTS)
113
, the resource manager
109
identifies the particular disk drive
103
in which the data requested by the channel adapter
104
is stored and the corresponding device adapter
106
which is connected to the identified disk drive. Thereafter, the resource manager
109
requests the device adapter
106
to store the object data to the cache memory or share storage
105
. Upon receiving the request from the resource manager
109
, the disk adapter
106
instructs the disk drive
103
which has the object data to transfer the data to the cache memory. The disk adapter
106
also inquires the cache function engine
107
for an area in the cache memory where the object data can be stored.
In response, the cache function engine
107
searches for a vacant area in the cache memory by referring to the cache table storage
112
, and notifies the device adapter
106
of the available storage area. The device adapter
106
then transfers the data from the disk drive
103
to the area specified by the cache function engine
107
. When the transfer of the object data is completed, the disk drive
103
notifies the disk adapter
106
. Once the device adapter
106
stores all the object data in the cache memory, it then notifies the cache function engine
107
and the resource manager
109
of the completion of the data transfer. The cache function engine
107
then updates the cache table storage
112
to reflect the storage of the object data in the cache memory.
Meanwhile, the resource manager
109
, which has received a message from the device adapter
106
that the object data has been transferred to the cache memory, notifies this event to the channel adapter
104
, which then inquires the cache function engine
107
again whether the object data is stored in the cache memory. In response, the cache function engine
107
again refers to the cache table storage
112
and judges whether the data inquired by the channel adapter
104
is stored in the cache memory or not, and then sends a message to channel adapter
104
. Here, since the object data has been stored in the cache memory by the device adapter
106
, the cache function engine
107
notifies the channel adapter
104
that the object data is stored in the cache memory. Upon receiving this notification, the channel adapter
104
transfers the data to the host apparatus
102
from the cache memory, thereby completing the response to the data request from the host apparatus.
Each of the groups “a” and “b” is also provided with service adapters (SA)
110
for conducting maintenance of each function module in their respective groups. The service adapter
110
sends data informing about a structure of the disk control device
101
to each function module, and conducts boot process and diagnostic process for each module also. The service adapter
110
is provided with a discrete disk drive
111
for storing various kinds of data necessary for performing the maintenance functions.
As the information processing systems grow to accommodate a greater number of host apparatus and disk drives, occurrences of disk control device failures resulting in the stoppage of the entire system become a very important problem. The file control devices
101
of the type described above, which have a structure that can be divided into duplicate groups, are effective in preventing system stoppage which occurs as a result of file control device failures. In the file control device of
FIG. 9
, the channel adapter
104
a,
the device adapter
106
a
and the share storage
105
a
of function group “a” are all connected to the common bus
108
a,
but not to the common bus
108
b,
which is electr
Ito Mikio
Kobayashi Tohru
Nishizono Shinichi
Chace C. P.
Ellis Kevin L.
Fujitsu Limited
Greer Burns & Crain Ltd.
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